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Water: Interim Enhanced Surface Water Treatment Rule

Fact Sheet on New Data Available on Microbials and Disinfection Byproducts

Notices of Data Availability for Stage 1 DBPR and IESWTR

The Environmental Protection Agency has published new data on two interrelated rulemaking efforts -- the Interim Enhanced Surface Water Treatment Rule (IESWTR) and the Stage 1 Disinfectants and Disinfection Byproducts Rule (DBPR). The EPA is developing these rules to control microbial pathogens, disinfectants and disinfection byproducts (DBPs) in drinking water. They will be the first drinking water regulations to specifically address the microbial pathogen, Cryptosporidium. The Safe Drinking Water Act (SDWA), as amended in 1996, requires the IESWTR and the DBPR to be finalized by November 1998. EPA proposed these rules in 1994 (Stage 1 DBPR at 59 FR 38668, July 29, 1994; IESWTR at 59 FR 38832, July 29, 1994).

Why are these two rules important, and how are they related?
Microbiological contaminants, such as bacteria, protozoa and viruses, are likely the greatest remaining health risk management challenge for drinking water suppliers, according to a 1990 report from EPA's Science Advisory Board. The control of microbiological contaminants is further complicated because commonly-used disinfection processes themselves may pose health risks. Conventional practices require the addition of disinfectant chemicals to the water that, while effective in controlling many harmful microorganisms, combine with organic and inorganic compounds in the water and form potentially harmful disinfectant byproducts (DBPs).

One of the most complex questions facing water supply professionals is how to minimize the risks from these DBPs and still control microbial contaminants. The IESWTR and DBPR would reduce the level of exposure from disinfectants and DBPs, without undermining the control of microbial pathogens. In doing so, the rules would ensure that drinking water is microbiologically safe, at the limits set for disinfectants and DBPs, and that these chemicals do not pose an unacceptable risk at these limits.

Why are there Notices of Data Availability?
At the time the two rules were proposed, in 1994, the EPA had insufficient data on issues related to microbial and DBP control. The intent was to gather additional information through a data collection effort (see Information Collection Rule) and additional research. The plan was to consider and make that information available for the public through a Notice of Data Availablity prior to final regulatory action. The 1996 amendments to SDWA established new deadlines which required a change in approach.

To help meet the deadlines for the IESWTR and Stage 1 DPBR and to maximize stakeholder participation, in February 1997, the Microbial/Disinfection Byproducts Advisory Committee was established under the Federal Advisory Committee Act. The goal of the group was to collect, share and analyze new information and data, and to build consensus on the regulatory implications of this new information. The committee consists of 17 members representing EPA, state and local public health and regulatory agencies, local elected officials, drinking water suppliers, chemical and equipment manufacturers, and public interest groups.

The Notices of Data Availability summarize the findings of the M/DBP Advisory Committee, and the its recommendations to the EPA, listed below. The recommendations are open for public comment until February 3, 1998.

What did the Microbial/Disinfection Byproducts Advisory Committee do?
The committee met five times, in March through July 1997, to discuss issues related to the IESWTR and Stage 1 DBPR. Technical support for these discussions was provided by a technical work group established by the committee at its first meeting. The committee's activities resulted in the collection, development, evaluation, and presentation of substantial new data and information related to key elements of both proposed rules.

What did the Advisory Committee recommend?
The committee reached agreement on nine major issues discussed in the Notices of Data Availability (NODA) for the Stage 1 DBPR and IESWTR published in the Federal Register. The Committee's recommendations to USEPA on these issues were contained in an Agreement In Principle document dated July 15, 1997. The following three issues contained in the Advisory Committee recommendations are discussed in the Stage 1 DBPR NODA:

  • no changes to the proposed Maximum Contaminant Levels (MCLs) for total trihalomethanes (TTHMs), haleoacetic acid 5 (HAA5) or bromate;
  • modifications to requirements for enhanced coagulation and enhanced softening; and
  • altering proposal to allow full credit towards disinfection requirements in the IESWTR for predisinfection.
The following issues contained in the advisory committee recommendations are discussed in the IESWTR NODA:

  • microbial benchmarking/profiling to provide a methodology and process by which a PWS and the State, working together, assure that there will be no significant reduction in microbial protection as the result of modifying disinfection practices in order to meet MCLs for TTHM and HAA5;
  • tighter combined filter effluent turbidity limits and individual filter monitoring;
  • Cryptosporidium MCLG;
  • removal of Cryptosporidium; and
  • expanding sanitary surveys.

In addition, the agency agreed to take a closer look at the role of Cryptosporidium inactivation as part of a multiple barrier concept. The notices also contain a discussion of the implications of the 1996 SDWA Amendments on the compliance schedules and options for how to maintain simultaneous compliance with pathogen control and DBP rules.

You can request a copy from the Safe Drinking Water Hotline at 800-426-4791; or see the , pages 59485-59557 (IESTWR), and pages 59387-59484 (DBPR).

We are looking for comments on all aspects of the NODAs, including any additional data and information, and are particularly interested in comments on the advisory committee recommendations to EPA and on the compliance schedule options. Comments must be received or postmarked by midnight date TBD. To submit comments by mail, please send an original and three copies of your comments (please submit separate comment sets for each NODA) and enclosures (including references), in hard copy or on a disc in WordPerfect 5.1 or 6.1 or ASCII file format, to:

DBPR (IESWTR) Comment Clerk
Water Docket (MC4101)
USEPA, 401 M St. SW
Washington, DC 20460

To submit comments electronically, (you can do this at Federal Depository Libraries):

  • Use ASCII format,
  • Avoid using special characters or encryption,
  • Specify which NODA (DBPR or IESWTR),
  • Send to: ow-docket@epamail.epa.gov

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